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Valve Modification

In a perfect world of valve supply and demand, an end-user would be able to purchase any combination of valve configurations from the distributor with only a few days notice. The commonly-stocked ‘standard trim’ valves would share shelf space with the most unusual trimmed or end-configured valves. However, in this world of globally procured commodity steel valves and ‘just-in-time’ inventories, it is not a financially viable option. So in order to meet the demand for these specials in the United States, the valve modification industry was created.

Valve modification can be defined as adding value to standard or commodity valves, generally gate, globe, check & ball valves, by the installation of special trims, end-connections, packing & gaskets and other accessories or upgrades not provided on the original product. All of these operations can of course be performed by the OEM; however the average required turnaround time on valve modification orders today is 5-7 working days, compared to the standard multi-week manufacturer’s lead times. These items are usually shorts that had been missed on the original project valve take-off lists or they are needed for routine MRO activity. In all cases, delivery time is of the essence and there is rarely enough time to allow for overseas shipping.


To understand the genesis of the valve modification industry in the United States, a little history is in order. Valve supply through the 50’s and 60’s was fairly steady and the procurement philosophy of the end-user was to order early and keep extras in stock. Virtually every plant on the Gulf Coast had a storehouse loaded with a variety of spare valves, including specials. But belt-tightening measures by the end-users, which lowered their inventories, combined with the petrochemical construction boom of the 70’s, exceeded the delivery capability of domestic manufacturers for commodity and particularly, “special” valves.

Faced with the expense of stocking a huge variety of slower-turning specials, the distributors would generally just stock “vanilla” valves and have a local valve shop re-trim or install new packing and gaskets to meet customer requirements. In those days, typical deliveries for modification orders were 4-6 weeks, due to the size of the orders. Comparatively, today’s modification work deliveries run less than a week. During this period, the OEM’s would tolerate the aftermarket work on their products because they were reaping the benefit of the sale of the stock valves.

In the late 70’s, the steel valve business in the United States began perhaps its most dramatic metamorphosis, as a new entity, the imported valve, made its way upon the American scene in force. Huge worldwide petrochemical and refining projects totally depleted the U.S. valve manufacturer’s production capacity and forced them to look elsewhere to meet domestic valve demand. Valves from Italy, Eastern Europe, Japan and Korea helped fill the gap. These imported valves were rarely brought into the U.S. in anything other than standard trim, so valve service companies prospered from the additional modification work they created.

Up until this time, the modification of a valve was generally frowned upon by the OEM’s. However, they soon began to see the advantages of auditing and authorizing quality valve service facilities to perform modification work on their products. With an official authorization program, the OEM would retain some oversight of the aftermarket work performed on their products, plus reduce the number of bogus operations performed on their valves.

There have been several lawsuits filed in the United States concerning unauthorized modification of OEM products. These suits were the result of poor workmanship which resulted in personal and/or property damage. Some examples of this bogus work include: welding overlays for sour service that received no PWHT and cracked in service; stems fabricated by welding the old (13 Cr) stem foot on to a new 316ss shaft and failing due to severe corrosion; cryogenic valves fabricated without design calculations that resulted in joint failure. The OEM authorization program has gone a long way in diminishing these kinds of claims.

The two pioneers of the authorized modification shop concept were Kitz & Velan, both of which began official authorization programs in the early 80’s. Relationships between OEM’s and authorized valve shops expanded further in the 90’s as well equipped authorized valve shops became essential tools in the overall OEM marketing focus.

Gaining OEM Approval

The most common way a valve shop is approved is through an audit process. The audit is normally conducted by the QA Manager of the OEM or an appointed audit team. At the very least, the audit will examine all of the quality and procedural documents of a potential organization. While ISO 9001 or 9002 certification is not required by the OEMs, an ISO or API Q1 based quality system is a must. Additionally, specific shop procedures are also reviewed. Needless to say having a good reputation in the industry is also helpful in gaining OEM approval. Virtually all of the quality modification shops in the United States are also members of the Valve Repair Council, an organization sponsored by the Valve Manufacturers Association of America.

In the US, the valve modification business is logically focused in the Gulf Coast area, where several major PVF distributors are headquartered. The proximity of the area refining and petrochemical industry also makes this location even more viable for valve modification companies. I would estimate that more new valve modification work is performed in the Houston area than in all of the other regions of the US combined.

‘Mod Shops’

Today’s valve modification service provider is a far cry from the blacksmith like valve shops of the 40’s and 50’s. Since the modification shop has to respond quickly, vertical integration is very important to the overall success of the shop. Walking through the doors of the highest caliber shops today, you will find manual and CNC machine tools, AutoCAD software, submerged-arc and fluxed-core welding, heat treatment furnaces of all sizes, in-house nondestructive evaluation and elaborate testing facilities, all tied together via sophisticated computer tracking systems. In-house engineering is also important and mechanical and welding engineers are likely to be found in many of these shops as well.

Just what types of work are performed in these facilities? Virtually any special valve that is offered by an OEM can be created in the best ‘mod-shops’ or trim-shops, as they are called in the Houston area. Here are few of the more common jobs performed regularly by United Valve, a leading provider of valve modification services in the Houston area:

Trim changes on cast and forged steel valves
Bore schedule changes on BWE valves
Raised face to RTJ ends
Cryogenic gas column fabrication
Elastomer seating inserts
Special packing & gaskets
Fugitive emissions upgrades
Bypass and drain valve attachment
Gear and actuator installation
Nondestructive evaluation (RT, PT & MT)
Casting repair & upgrade
API RP591 qualification testing
Hydrostatic testing
Fugitive emissions testing
Cryogenic testing

A Case History

United Valve performed a modification for an OEM recently which characterizes the modification process very well. After supplying cryogenic valves manufactured to OEM design specifications, it was discovered that the OEM design was not acceptable to the end-user because of some very specific service requirements that went above and beyond the standard product. We then were asked to make the valves conform to the customers needs. This required a new joint design and complete engineering calculations of the new joint assembly. In addition, X-ray radiography procedures needed to be developed to shoot the unusual configuration and yield a readable image.

All of the engineering work was performed in-house and the job proceeded on schedule. The fabrication work met all of the customer inspection requirements and the NDE department performed the radiography to the customer’s satisfaction. The result was that a thorny problem was solved for both the end-user and the OEM, all because a qualified, authorized modification shop was available to perform the work.

OEM Support

OEM support is critical to the success of an authorized modification facility. Since time is of the essence in most modification orders, good communication between engineering departments is a must. A level of trust and confidence must also be built up between the mod shop and OEM in order for the system to function effectively. After a strong relationship has been built, the amount and scope of engineering data provided to the mod shop increases dramatically. But the information stream of valuable information flows back to the OEM as well.

The mod shop is a valuable source of valve quality feedback to the OEM. On the floor of a typical shop, thousands of valves are tested and inspected each year. At United Valve, for example, we have developed an elaborate non-conformance database program that provides very detailed information on every OEM valve failure. This data is then complied and periodically reported back to the OEM for corrective action.

The valve shop also serves as the final inspection point for OEM products. In several cases, defects have been discovered that could have had dire consequences for the manufacturer, had they failed in service.

The question of warranty often comes up when discussing mod shops and OEM’s. Generally, the manufacturer warrants the work that they are responsible for, while the mod shop warrants only the work that they are responsible for. For example, a stem failure on a BWE valve that received only a bore change by the mod shop would be covered by the OEM. However, a poor weld in a weld built-up bore change that failed end-user radiography would be the responsibility of the mod shop. There are also a few OEM’s that state that their warranty covers everything that the authorized shop does to their valves.

Although some manufacturers are now setting up service centers to repair and modify their products, the majority of valve modification work is still performed by independent valve modification shops. The independent shops usually have the edge in service and order turnaround, because they are not encumbered by a large OEM bureaucracy.

Valve modification shops provide an important service to end-users, distributors and OEM’s. The OEM benefits by being able to concentrate on high production items, rather than specials that often slow assembly lines down. The distributor benefits by spending less money stocking slow moving special valves. And the OEM benefits by receiving critical, special valves on-time and at a reasonable price, which lowers his total cost of ownership. The concept of OEM authorized valve modification is a winner for everyone involved!

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